Contact detecting device and display device having detection lines of different lengths

ABSTRACT

A contact detecting device including: a contact responding section configured to produce an electric change in response to an object to be detected coming into contact with or proximity to a detecting surface; and a contact driving scanning section configured to scan application of driving voltage to the contact responding section in one direction within the detecting surface, and control output of the electric change in time series, wherein the contact driving scanning section performs a plurality of scans of different regions of the contact responding section in parallel with each other, and outputs a plurality of the electric changes in parallel with each other.

CROSS REFERENCES TO RELATED APPLICATIONS

The subject matter of application Ser. No. 12/550,105, is incorporatedherein by reference. The present application is a Continuation of U.S.Ser. No. 12/550,105, filed Aug. 28, 2009, which claims priority toJapanese Patent Application JP 2008-236931 filed in the Japanese PatentOffice on Sep. 16, 2008, the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a contact detecting device detectingthat a user brings a finger, a pen or the like into contact with orproximity to a detecting surface. The present invention also relates toa display device having functions of the contact detecting device withina display section.

2. Description of the Related Art

A contact detecting device referred to as a so-called touch panel isknown.

The contact detecting device is generally a device detecting that afinger of a user, a pen or the like comes into contact with or proximityto a detecting surface.

On the other hand, the touch panel is formed on a display panel, andenables information input as a substitute for ordinary buttons by makingvarious buttons displayed as an image on a display surface. Applicationof this technology to a small mobile device enables a display and abutton arrangement to be shared, and provides great advantages ofincreasing the size of the screen or saving the space of an operatingsection and reducing the number of parts.

Thus, the “touch panel” generally refers to a panel-shaped contactdetecting device combined with a display device.

Three contact detecting systems of the touch panel are known, which arean optical type, a resistive film type, and a capacitance type.

To associate an electric change occurring in response to contact orproximity with positional information needs a large number of pieces ofwiring combined so as to enable position identification and arranged inthe form of a matrix.

To increase the resolution of detection by a manner of positiondetection with this wiring combination needs an enormous number ofpieces of wiring.

Thus, in the three detecting systems mentioned above, a driving methodthat detects a contact position or a proximity position while scanninglines that output an electric change in one direction is becomingmainstream (see Hirotaka Hayashi etc., “Optical Sensor Embedded InputDisplay Usable under High-Ambient-Light Conditions,” SID 07 DIGEST p.1105 (optical type), Bong Hyun You etc., “12.1-inch a-Si:H TFT LCD withEmbedded Touch Screen Panel,” SID 08 DIGEST p. 830 (resistive filmtype), and Joohyung Lee etc., “Hybrid Touch Screen Panel Integrated inTFT-LCD,” SID 08 DIGEST p. 834 (capacitance type), hereinafter referredto as Non-Patent Documents 1 to 3, respectively, for example). A line inthis case refers to a row in an X-direction or a Y-direction of minutesensor parts arranged two-dimensionally by a predetermined rule forcontact detection.

When the touch panel is provided on the display panel, the thickness ofa display module as a whole is increased.

Accordingly, the mainstream of developed types has recently changed froma touch panel mounted onto a display panel to a touch panel includedwithin a display panel (see the above Non-Patent Documents 1 to 3 andJapanese Patent Laid-Open No. 2008-9750).

A “display device provided with a touch sensor” will hereinafter be usedas a designation regardless of whether the touch panel is mounted onto adisplay panel or whether the touch panel is formed integrally with thedisplay panel.

SUMMARY OF THE INVENTION

The driving method of driving a contact detecting device in each linerequires high-speed scanning of lines along one or both of an X-axisdirection and a Y-axis direction. The contact detecting device thus hasa very high driving frequency or the like and involves very high powerconsumption or the like, which is to be remedied.

On the other hand, in a display device provided with a touch sensor as acombination of a display device and a contact detecting device, inparticular, detection driving frequency may be limited by displaydriving frequency, and thus the detection driving frequency may not beable to be determined freely.

The inventor of the present application has proposed a technique forreducing the thickness of a display device by using a pixel electrodefor liquid crystal display also as one detecting electrode of acapacitance detection system (see Japanese Patent Application No.2008-104079, for example). In this case, display driving frequency anddetection driving frequency coincide with each other for structuralreasons.

However, this technique has a disadvantage in that the detection drivingfrequency cannot be changed freely due to a limitation of the displaydriving frequency even when the detection driving frequency is to beincreased because of low detection speed and poor response toinformation input.

The present invention provides a contact detecting device improved indetection speed without increasing the detection driving frequency. Thepresent invention also provides a display device provided with a contactdetecting function which device has a structure allowing the detectiondriving frequency to be determined arbitrarily with a minimum limitationby display driving in a case of low detection speed and poor response toinformation input or in a converse case.

A contact detecting device according to an embodiment of the presentinvention includes a contact responding section and a contact drivingscanning section.

The contact responding section produces an electric change in responseto an object to be detected coming into contact with or proximity to adetecting surface.

The contact driving scanning section scans application of drivingvoltage to the contact responding section in one direction within thedetecting surface, and controls output of the electric change in timeseries. At this time, the contact driving scanning section performs aplurality of scans of different regions of the contact respondingsection in parallel with each other, and outputs a plurality of electricchanges in parallel with each other.

In the contact detecting device having such a constitution, the contactdriving scanning section performs a plurality of scans of differentregions of the contact responding section in parallel with each other,and therefore scanning driving frequency is lower than in a case ofscanning the whole of the contact responding section. Alternatively,when the scanning driving frequency is the same, the speed of contactdetection is high, that is, a time taken to complete one scan of thecontact responding section is short.

In the present invention, preferably, the contact detecting devicefurther includes a detecting line group arranged in a form of parallelstripes that are long in a direction of scanning of the contactresponding section, and a detecting section configured to detectoccurrence of the electric change from a voltage change in the detectingline group, and identify a position of the occurrence. In addition, atleast one of a manner of intersecting the plurality of regions of thecontact responding section by the detecting line group and a manner ofdriving the plurality of regions by the contact driving scanning sectiondiffers between the regions.

The detecting section identifies one of the plurality of regions withwhich region the object to be detected is in contact or to which regionthe object to be detected is in proximity on a basis of a voltage changepattern of a detecting line, the voltage change pattern occurringaccording to difference in at least one of the manner of theintersecting and the manner of the driving between the regions.

This preferable constitution is to overcome a difficulty in identifyinga region that the object to be detected is in contact with (or inproximity to) when the plurality of scans are performed simultaneouslyin parallel with each other and electric changes are output from theidentical detecting line group.

However, this constitution is not necessary provided that contact (orproximity) occurs at one position. Also when the detecting line group isseparated completely in each region, this constitution is not necessarybecause the above identification is easy.

In the preferable constitution described above, at least one of themanner of intersecting the plurality of regions by the detecting linegroup and the manner of driving the plurality of regions by the contactdriving scanning section differs between the regions. Thus, according tothis difference, the voltage change pattern occurring in a detectingline when contact with (or proximity to) the different regions is madediffers. The detecting section identifies a region that an object to bedetected is in contact with (or in proximity to) from the voltage changepattern, and identifies the position of the contact (or proximity).

More specifically and preferably, at least one of a phase and anamplitude of the driving voltage output by the contact driving scanningsection differs between the plurality of regions, and the detectingsection is connected to one end in the scanning direction of thedetecting line group and identifies one of the plurality of regions withwhich region the object to be detected is in contact or to which regionthe object to be detected is in proximity on the basis of the voltagechange pattern of the detecting line, the voltage change patternoccurring according to difference in the driving voltage.

Alternatively, when the detecting line group is separated completely asdescribed above, the contact detecting device preferably includes twosets of a predetermined number of detecting lines, the detecting linesbeing long in the scanning direction of the contact responding sectionand being in a form of parallel stripes, and two detecting sections eachconnected to the predetermined number of detecting lines of thecorresponding set at one end in the scanning direction, the twodetecting sections each detecting occurrence of the electric change on abasis of a voltage change pattern occurring in the predetermined numberof detecting lines of the corresponding set and identifying a positionof the occurrence.

A display device according to an embodiment of the present inventionincludes a display section and a display driving scanning section. Thedisplay section subjects an amount of transmitted light to lightmodulation according to an input video signal, and outputs light afterthe modulation from a display surface. When a row in one direction ofpixels as minimum units of the light modulation of the display sectionis a line, the display driving scanning section scans an operation ofapplying driving voltage for the light modulation to each line inanother direction orthogonal to the line.

In the display device, a contact responding section configured toproduce an electric change in response to an object to be detectedcoming into contact with or proximity to the display surface is formedwithin the display section. In addition, the display driving scanningsection doubles as a contact driving scanning section configured to scanapplication of driving voltage to the contact responding section in onedirection within the display surface, and control output of the electricchange in time series. The contact driving scanning section performs aplurality of scans of different regions of the contact respondingsection in parallel with each other, and outputs a plurality of electricchanges in parallel with each other.

According to the display device having the above constitution, thecontact responding section is formed within the display section, and thedisplay driving scanning section doubles as the contact driving scanningsection so as to be able to perform scanning at a time of displaydriving and scanning at a time of contact driving in parallel with eachother. Thus, a space within a display panel is used effectively, andconstitutions within the panel can be shared as much as possible.

According to the present invention, the present invention can provide acontact detecting device improved in detection speed without increasingthe detection driving frequency.

In addition, according to the present invention, it is possible toprovide a display device provided with a contact detecting functionwhich device has a structure allowing the detection driving frequency tobe determined arbitrarily in a case of low detection speed and poorresponse to information input or with a minimum limitation by displaydriving in a converse case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are an equivalent circuit diagram and a schematicsectional view of assistance in explaining the operation of a touchsensor section according to a first to a sixth embodiment;

FIGS. 2A and 2B are a similar equivalent circuit diagram and a similarschematic sectional view when a finger is in contact with or inproximity to the touch sensor section shown in FIGS. 1A and 1B;

FIGS. 3A, 3B, and 3C are diagrams showing input-output waveforms of thetouch sensor sections according to the first to sixth embodiments;

FIGS. 4A, 4B, 4C, and 4D are plan views and a schematic sectional viewspecialized for an arrangement of electrodes for touch detection of adisplay device according to the first embodiment and circuits fordriving the electrodes and for detection;

FIG. 5 is a diagram showing an example of circuits of analternating-current signal source for sensor driving and a voltagedetector in display devices according to the first to sixth embodiments;

FIG. 6 is a diagram showing opposite-phase driving and responsewaveforms of a detecting line in the first embodiment;

FIG. 7 is a diagram showing driving with different amplitudes andresponse waveforms of a detecting line in the second embodiment;

FIG. 8 is a diagram in a case where kinds of amplitude of drivingvoltage are further increased in the second embodiment;

FIG. 9 is a diagram showing in detail the potential levels of theresponse waveforms in FIG. 8;

FIG. 10 is a diagram showing opposite-phase driving and responsewaveforms of a detecting line in the third embodiment;

FIG. 11 is a diagram showing in-phase driving and response waveforms ofa detecting line in the third embodiment;

FIG. 12 is a diagram showing an arrangement of detecting lines anddetecting circuits in the fourth embodiment;

FIG. 13 is an equivalent circuit diagram of a pixel in the displaydevices according to the fifth and sixth embodiments;

FIGS. 14A, 14B, 14C, and 14D are plan views and a schematic sectionalview specialized for an arrangement of electrodes for touch detection ofthe display device according to the fifth embodiment and circuits fordriving the electrodes and for detection;

FIGS. 15A, 15B, and 15C are diagrams showing a pattern of counterelectrodes according to the fifth embodiment, an equivalent circuit of atouch sensor section including the pattern, and an equation of a sensorvoltage;

FIGS. 16A, 16B, and 16C are plan views of a state of selection ofcounter electrodes (determination of an electrode group simultaneouslysubjected to alternating-current driving) according to the fifthembodiment and shifting (reselection) of the counter electrodes;

FIG. 17 is a schematic sectional view of the display device according tothe sixth embodiment;

FIGS. 18A and 18B are diagrams of assistance in explaining the operationof an FFS mode liquid crystal element according to the sixth embodiment;and

FIGS. 19A and 19B are diagrams showing the operation in FIGS. 18A and18B in section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will hereinafter bedescribed with reference to the drawings taking a contact detectingdevice of a capacitance type and a liquid crystal display device havinga function of such contact detection as main examples. Incidentally, thepresent invention is also applicable to a resistive film type and anoptical type. In addition, while a liquid crystal display device ishereinafter taken as an example, the present invention is alsoapplicable to other display devices such as an organic EL display deviceand the like.

The basics of capacitance type contact detection will be described as anitem on which embodiments are premised with reference to FIGS. 1A to 3C.

FIG. 1A and FIG. 2A are equivalent circuit diagrams of a touch sensorsection. FIG. 1B and FIG. 2B are diagrams of structure (schematicsectional view) of the touch sensor section. FIGS. 1A and 1B represent acase where a finger as an object to be detected is not in proximity to asensor. FIGS. 2A and 23 represent a case where the finger is inproximity to or in contact with the sensor.

The illustrated touch sensor section is a capacitance type touch sensor,and is composed of a capacitive element, as shown in FIG. 1B and FIG.2B. Specifically, the capacitive element (capacitance) C1 is formed of adielectric D and a pair of electrodes arranged so as to be opposed toeach other with the dielectric D interposed between the electrodes, thatis, a driving electrode E1 and a detecting electrode E2.

As shown in FIG. 1A and FIG. 2A, the driving electrode E1 of thecapacitive element C1 is connected to a driving signal source S thatgenerates an AC pulse signal Sg. The detecting electrode E2 of thecapacitive element C1 is connected to a voltage detector DET. At thistime, the detecting electrode E2 is grounded via a resistance R, wherebya DC level is electrically fixed.

The AC pulse signal Sg of a predetermined frequency, for example a few[kHz] to a few ten [kHz] is applied from the driving signal source S tothe driving electrode E1. The waveform of the AC pulse signal Sg isillustrated in FIG. 3B.

In response to the application of the AC pulse signal Sg, a signal(detection signal Vdet) of an output waveform shown in FIG. 3A appearsin the detecting electrode E2.

Incidentally, as will be described later in detail, in an embodiment ofa liquid crystal display device having the function of a contactdetecting device within a liquid crystal display panel, the drivingelectrode E1 corresponds to a counter electrode for liquid crystaldriving (electrode that is opposed to pixel electrodes and which iscommon to a plurality of pixels). In this case, for liquid crystaldriving, the counter electrode is subjected to alternating-currentdriving referred to as so-called Vcom inversion driving. Thus, inembodiments of the present invention, a common driving signal Vcom forthe Vcom inversion driving is used also as the AC pulse signal Sg fordriving the driving electrode E1 for the touch sensor.

In a state shown in FIGS. 1A and 1B in which a finger is not in contact,the driving electrode E1 of the capacitive element C1 is driven byalternating current, and an alternating-current detection signal Vdetappears in the detecting electrode E2 with the charging and dischargingof the driving electrode E1. The detection signal at this time willhereinafter be written as an “initial detection signal Vdet0.” Thedetecting electrode E2 side is DC-grounded, but is not grounded in termsof high frequency. Therefore, there is no discharge path of alternatingcurrent, and the pulse peak value of the initial detection signal Vdet0is relatively high. However, when a time passes after the rising of theAC pulse signal Sg, the pulse peak value of the initial detection signalVdet0 gradually decreases due to a loss. FIG. 3C shows a waveform in anenlarged state together with a scale. The pulse peak value of theinitial detection signal Vdet0 decreases by about 0.5 [V] from aninitial value of 2.8 [V] with the passage of a short time due to ahigh-frequency loss.

When the finger comes into contact with the detecting electrode E2 orapproaches the detecting electrode E2 to a close range so as to affectthe detecting electrode E2 from the initial state, as shown in FIG. 2A,a circuit state changes to a state equivalent to that of a capacitiveelement C2 being connected to the detecting electrode E2. This isbecause a human body is equivalent to a capacitance having one sidegrounded in terms of high frequency.

In this contact state, a discharge path of an alternating-current signalvia the capacitive elements C1 and C2 is formed. Thus, with the chargingand discharging of the capacitive elements C1 and C2, alternatingcurrents I1 and I2 flow through the capacitive elements C1 and C2,respectively. Therefore the initial detection signal Vdet0 isvoltage-divided into a value determined by a ratio between thecapacitive elements C1 and C2 or the like, and the pulse peak valuedecreases.

A detection signal Vdet1 shown in FIG. 3A and FIG. 3C appears in thedetecting electrode E2 when the finger comes into contact. FIG. 3C showsthat an amount of decrease of the detection signal is about 0.5 [V] to0.8 [V].

The voltage detector DET shown in FIGS. 1A and 1B and FIGS. 2A and 2Bdetects the contact of the finger by detecting the decrease in detectionsignal using a threshold value Vth, for example.

First Embodiment

In the present embodiment, description will be made of an embodiment ofa contact detecting device according to the present invention by takinga capacitance type touch panel externally attachable to a display panelas an example.

FIGS. 4A to 4C are plan views specialized for an arrangement ofelectrodes of the contact detecting device according to the presentembodiment and circuits for driving the electrodes and for detection.FIG. 4D schematically shows a sectional structure when the contactdetecting device according to the present embodiment is externallyattached to the display surface side of a liquid crystal display device.FIG. 4D shows a section of six pixels in a row direction (pixel displayline direction), for example.

In FIG. 4D, for easy viewing of the sectional structure, counterelectrodes, pixel electrodes, and detecting electrodes are hatched,whereas hatching of other parts (substrates, insulating films,functional films and the like) is omitted. The omission of the hatchingis similarly made in other subsequent diagrams of sectional structure.

Incidentally, details of the liquid crystal display device shown in FIG.4D will be described later in another embodiment. Thus, while referencesused in the description are added in FIG. 4D, detailed description ofthe liquid crystal display device itself will be omitted in the presentembodiment.

The liquid crystal display device shown in FIG. 4D includes a substratesupplied mainly with signals for driving pixels (which substrate willhereinafter be referred to as a driving substrate 2), a countersubstrate 4 disposed so as to be opposed to the driving substrate 2, anda liquid crystal layer 6 disposed between the driving substrate 2 andthe counter substrate 4.

The contact detecting device according to the present embodiment (whichdevice will hereinafter be referred to as a touch panel 10) is laminatedonto the counter substrate 4 via an adhesive layer 12.

The touch panel 10 includes a driving electrode E1 on the side of theliquid crystal display device and a detecting electrode E2 overlappingthe driving electrode E1 with a dielectric layer 14 interposed betweenthe driving electrode E1 and the detecting electrode E2. A protectivelayer 13 is formed on the detecting electrode E2.

A “detecting surface 13A” refers to an outermost surface of theprotective layer 13.

In a state in which the touch panel 10 is laminated on the liquidcrystal display device 1 as shown in FIG. 4D, display light is emittedto a user side through the touch panel 10, and therefore the detectingsurface 13A is a display surface.

A “contact responding section” refers to a part where when a userperforms an operation of bringing an object to be detected such as afinger, a pen or the like into contact with or into proximity to thedetecting surface 13A, an electric change occurs in response to theoperation. Thus, as is clear from correspondence with FIGS. 1A to 3C, aconstitution for effecting a potential change in response to the contactor the proximity as described above, that is, a part including at leastthe driving electrode E1, the detecting electrode E2, and the dielectriclayer 14 between the driving electrode E1 and the detecting electrode E2in the present example corresponds to an embodiment of the “contactresponding section.”

As shown in FIGS. 4A to 4C, the driving electrode E1 and the detectingelectrode E2 are divided in directions orthogonal to each other.

When the detecting surface 13A is viewed from the user side, the“contact responding section” is divided into a plurality of regions, forexample a first region Re1 and a second region Re2, as shown in FIG. 4A.A predetermined number m of driving electrodes E1 are arranged in eachof the first region Re1 and the second region Re2. In FIG. 4A, thedriving electrodes E1 of the first region Re1 are indicated byreferences “E11_1 to E11 _(—) m,” and the driving electrodes E1 of thesecond region Re2 are indicated by references “E12_1 to E12 _(—) m.”

The driving electrodes E11_1 to E11 _(—) m or E12_1 to E12 _(—) m have astripe shape of a relatively large width, and are arranged in parallelwith each other.

The driving electrodes E11_1 to E11 _(—) m form a first set EU11 ofdriving electrodes. The driving electrodes E12_1 to E12 _(—) m form asecond set EU12 of driving electrodes.

On the other hand, the detecting electrode E2 is formed of apredetermined number k of conductive layers in a parallel stripearrangement that is long in a direction orthogonal to the drivingelectrode E1. Each of the detecting electrodes in the shape of parallelstripes will hereinafter be referred to as a “detecting line.” In FIGS.4B and 4C, the detecting lines are indicated by references “E2_1 to E2_(—) k.”

The k detecting lines E2_1 to E2 _(—) k form one set EU2 of detectinglines. One set of detecting lines is arranged in the present embodiment.Thus, in the present embodiment, the set of detecting lines(predetermined number k of detecting lines) intersects each of the firstregion Re1 and the second region Re2 in a same manner. Morespecifically, a mode of overlap between the driving electrodes and thedetecting lines is the same in the first region Re1 and the secondregion Re2.

A detecting circuit 8 as a “detecting section” is connected to one endof the k detecting lines E2_1 to E2 _(—) k arranged as described above.The detecting circuit 8 has the voltage detector DET shown in FIGS. 1Aand 1B and FIGS. 2A and 2B as a basic detection unit. A detection signalVdet (see FIGS. 3A to 3C) is input from each of the k detecting linesE2_1 to E2 _(—) k to a corresponding voltage detector DET in thedetecting circuit 8.

A contact driving scanning section 11 is connected to the drivingelectrodes E11_1 to E12 _(—) m.

A significant feature of the present invention is that the contactdriving scanning section 11 scans a driving voltage in the first regionRe1 and the second region Re2 separately and in parallel. By performingthis parallel scanning, the contact driving scanning section 11 outputsan electric change occurring in the “contact responding section” inresponse to contact or proximity of an object to be detected, that is, apotential change in a detecting line in this case in parallel.

FIG. 5 is a diagram showing an example of configuration of the detectingcircuit 8 performing a touch detecting operation together with anelectrode pattern indicating the position of a detection object.

In FIG. 5, the driving electrode E11_1 indicated by hatching is selectedby being connected to a driving signal source S, and other nonselecteddriving electrodes E11_2 to E11_5 are retained at a GND potential. Astate in which a driving electrode is selected is referred to also as anon state, and a state in which a driving electrode is not selected isreferred to also as an off state.

FIG. 5 shows a circuit diagram of the voltage detector DET and thedriving signal source S connected to a detecting line E2 _(—) i (i=l tok) intersecting the group of these driving electrodes. Capacitiveelements C1_1 to C1_5 are formed in respective parts of intersection ofthe detecting line E2 _(—) i and respective counter electrodes.Incidentally, in the present embodiment, the first set EU11 of m drivingelectrodes and the second set EU12 of m driving electrodes are actuallydriven in parallel as described above.

The driving signal source S illustrated in FIG. 5 has a controllingsection 91, two switches SW(+) and SW(−), a latch circuit 92, a buffercircuit (waveform shaping section) 93, and an output switch SW.

The controlling section 91 is a circuit that controls the two switchesSW(+) and SW(−) for switching a positive voltage V(+) and a negativevoltage V(−) and the output switch SW. The controlling section 91 can bereplaced by an external CPU or the like without being provided withinthe driving signal source S.

The switch SW(+) is connected between the positive voltage V(+) and aninput of the latch circuit 92. The switch SW(−) is connected between thenegative voltage V(−) and an input of the latch circuit 92. The outputof the latch circuit 92 is connected to the on-side node of the outputswitch SW via the buffer circuit 93. The buffer circuit 93 subjects thepositive voltage V(+) and the negative voltage V(−) to potentialcompensation with an input potential, and then outputs the positivevoltage V(+) and the negative voltage V(−).

The output switch SW is controlled by the controlling section 91 todetermine whether to turn the corresponding driving signal source S on(a selected state or an active state) or to set the correspondingdriving signal source S in an inactive state by GND connection. Becauseof synchronization with the control of other driving signal sources S,this function of the controlling section 91 is generally performed byfor example a constitution in which a signal for shifting and selectinga group of driving signal sources S to be activated is passed on by ashift register or the like.

The detecting line E2 to which the capacitive elements C1_1 to C1_5 areconnected is connected with a voltage detector DET.

The voltage detector DET illustrated in FIG. 5 includes an OP amplifiercircuit 81, a rectifying circuit 82, and an output circuit 83.

The OP amplifier circuit 81 is formed by an OP amplifier 84, resistancesR1 and R2, and a capacitance C3 as shown in FIG. 5. The OP amplifiercircuit 81 forms a filter circuit for removing noise. This filtercircuit has an amplification factor determined by a ratio between theresistances or the like, and functions also as a signal amplifyingcircuit.

The detecting line E2 is connected to the non-inverting input “+” of theOP amplifier 84. A detection signal Vdet is input from the detectingline E2. The detecting line E2 is connected to a ground potential via aresistance R so that the DC level of the potential of the detecting lineE2 is electrically fixed. The resistance R2 and the capacitance C3 areconnected in parallel with each other between the output and theinverting input “−” of the OP amplifier 84. The resistance R1 isconnected between the inverting input “−” of the OP amplifier 84 and theground potential.

The rectifying circuit 82 has a diode D1 for performing half-waverectification, a charging capacitor C4, and a discharging resistance R0.The anode of the diode D1 is connected to the output of the OP amplifiercircuit 81. The charging capacitor C4 and the discharging resistance R0are each connected between the cathode of the diode D1 and the groundpotential. The charging capacitor C4 and the discharging resistance R0form a smoothing circuit.

The potential of the cathode of the diode D1 (output of the rectifyingcircuit 82) is read as a digital value via the output circuit 83. Only acomparator 85 for performing voltage comparison with a threshold valueis shown in the output circuit 83 shown in FIG. 5. The output circuit 83also has a function of an AD converter. The AD converter may be of anarbitrary converter type such as a resistance ladder type, a capacitancedivision type or the like. The output circuit 83 compares an inputanalog signal with a threshold value Vth (see FIG. 3A) by the comparator85. The comparator 85 may be realized as a function of a control circuit(not shown) such as a CPU or the like. A result of the comparison isused by various applications as a signal indicating whether the touchpanel is touched, for example a signal indicating whether a buttonoperation is performed.

The threshold value Vt as a reference voltage for the comparator 85 canbe changed by a control section such as a CPU or the like, and therebythe potential of the detection signal Vdet can be determined.

Description will be returned to FIGS. 4A to 4D.

The contact driving scanning section 11 shown in FIGS. 4A to 4D has adriving signal source S and an inverted driving signal source Sx thatoutputs a driving voltage inverted in phase with respect to that of thedriving signal source S.

The contact driving scanning section 11 performs alternating-currentdriving of the first set EU11 of driving electrodes in the first regionRe1 by the driving signal source S, and performs alternating-currentdriving of the second set EU12 of driving electrodes by the inverteddriving signal source Sx. The objects of the alternating-current drivingare sequentially shifted in one direction in driving electrode units,whereby scanning is performed. While the scanning is performed in thesame direction in FIGS. 4A to 4D, the scanning may be performed inopposite directions. In addition, back-and-forth scanning of both thefirst set EU11 and the second set EU12 may be repeated. Alternatively, ablanking period may be provided, and scanning of both the first set EU11and the second set EU12 may be repeated with one same end as a startingpoint.

FIG. 6 shows opposite-phase driving and the response waveforms of adetecting line in the present embodiment.

Incidentally, the “response waveforms” in FIG. 6 schematically representa change component of a detection signal Vdet at a time of so-calledimpulse response in which a finger 100 is brought into contact with thedetecting surface 13A (see FIG. 4D) only for a very short time and istaken off immediately.

A driving voltage in scanning the first set EU11 of driving electrodes(operation of shifting the application of the driving voltage) in thefirst region Re1 shown in FIG. 6 is opposite in phase from a drivingvoltage in scanning the second set EU12 of driving electrodes in thesecond region Re2. When contact is made simultaneously at a position(point A) in the first region Re1 and a position (point B) in the secondregion Re2 which positions correspond to the same detecting line(written as “A+B”), no response waveform occurs, or even if a responsewaveform occurs, the response waveform is so small as to be negligible.The same is true for a case where no contact is made at either point(written as “untouched”).

On the other hand, when potential is lowered as shown in FIG. 6 due tocontact at point A, a potential change in which the potential risesoccurs at point B. Conversely, when the potential rises due to contactat point A, the potential decreases at point B. On the other hand, inthe case of simultaneous contact at points A and B, the positivepotential and the negative potential cancel each other out, so thatapparently no potential change occurs in the detecting line.

The “detecting section” including the detecting circuit 8 and a CPU orthe like not shown in the figure first determines the x-directionaddress of a contact position by determining in which of the k detectinglines a potential change has occurred. In addition, the detectingsection determines the y-direction address of the contact position fromthe timing of scanning and the timing of a change in output. At thistime, whether contact has been made in the first region Re1 or whethercontact has been made in the second region Re2 can be determined on thebasis of a degree of occurrence of the potential change, that is,positive polarity or negative polarity. Incidentally, because it is veryrare that timings and contact times of contact with two points areexactly the same, some response waveform occurs even in the case ofsimultaneous contact, and it can also be determined that thesimultaneous contact with the two points has occurred in the case of apattern of occurrence of the response waveform, for example a case wherea positive potential change and a negative potential change occurconsecutively.

In FIG. 6, “WRITING+DRIVING BORDER” is displayed in the first regionRe1, and “DRIVING BORDER” is displayed in the second region Re2. Thisdisplay means that the writing of a video signal for display on theliquid crystal display device 1 is started in the first region Re1, andthat contact driving scanning is started in parallel in the first regionRe1 and the second region Re2. While thus synchronizing contact drivingwith display driving is optional, synchronizing contact driving anddisplay driving with each other is desirable because of an advantage ofsharing a scanning driving section.

Advantages of the present embodiment will next be described.

The present embodiment can greatly reduce the time of one scan byperforming driving scanning for contact detection twice or more inparallel within a same time.

On the other hand, when the present invention is not applied, that is,when one scan is performed using all of one frame (F) of the touch panel10, the frequency of the scan is 60 Hz (the time of one scan for 1 F is16.7 [msec]).

However, in such a case, when a screen is touched immediately after ascan is passed, the touch is detected 33.4 (=16.7×2) [msec] after thetouch, and the touching of the screen is recognized only aftersubsequent processing in the CPU or the like. On the basis of therecognition, an image is changed according to an application, and in acase of an operating switch, the switch is turned on or off.

For example, application software processing after a touch is said totake about 50 to 100 [msec], and a response transmitted to a user takesas long as about 100 [msec]. The user feels that this response is veryslow, and feels stress.

When display is synchronized with the detection of the touch panel, amethod of increasing the frequency of frames to be written is consideredin order to alleviate a delay from the touch to the appearance ofresponse.

However, when the writing frequency is increased, a writing defectoccurs, and image processing with a heavy processing load or the like isnecessary. Because an image needs to be created from a signal of 60[Hz], for example, disadvantages such as large-scale image processing, asubstantial increase in power consumption, and the like are incurred.

In the present embodiment, two or more driving lines of the touch panelare scanned simultaneously, writing for display is performed by only oneof the driving lines, and the other performs alternating-current drivingof only driving electrodes for contact detection without the writingbeing involved.

Therefore the scan frequency of the touch panel can be doubled when twodetection driving scans are performed simultaneously, and tripled whenthree detection driving scans are performed simultaneously.Incidentally, two regions for inversion driving are provided in theabove example. In general, however, when N regions are provided, thephase of the driving voltages is preferably shifted by each of N equalparts of one cycle. In this case, determination may be difficult withonly the positive polarity and the negative polarity of changes inpotential of the detecting line. In this case, a region in which contacthas occurred can be identified by determining the level of the potentialchanges in addition to polarity while changing the reference potentialof the comparator shown in FIG. 5.

Incidentally, synchronization with the writing of the display devicedoes not necessarily need to be achieved. Even in that case, because thedriving frequency of contact detection is decreased, power consumptionis correspondingly reduced, or the response of the touch panel can beenhanced.

Second Embodiment

In the present embodiment, in a case of a plurality of regions, forexample a case where the number of regions is two, contact drivingvoltages having different amplitude levels are supplied to a firstregion Re1 and a second region Re2.

FIG. 7 shows response waveforms when the number of regions and thenumber of amplitude levels are two. FIG. 8 and FIG. 9 show responsewaveforms when the number of regions and the number of amplitude levelsare three.

In the embodiment shown in FIG. 7, a driving voltage supplied to a firstset EU11 of driving electrodes in the first region Re1 is different inamplitude from a driving voltage supplied to a second set EU12 ofdriving electrodes in the second region Re2. FIG. 7 illustrates a casewhere the amplitude of the latter driving voltage is substantially twicethe amplitude of the former driving voltage. The two driving voltagesare in phase with each other.

The second embodiment is the same as the first embodiment except thatthe driving voltages are in phase with each other and have the amplitudedifference. Therefore, FIGS. 4A to 4D are applied also to the secondembodiment except that the contact driving scanning section 11 in FIGS.4A to 4D has an in-phase alternating-current signal source for doublethe amplitude in place of the inverted driving signal source Sx. Inaddition, FIG. 5 is similarly applied.

As shown in FIG. 7, the peak value of a response waveform in the case ofnon-contact (untouched) is highest. A response waveform in a case wherepoint A on the side of a small driving amplitude (first region Re1) istouched has a next highest peak value. A response waveform in a casewhere point B on the side of a large driving amplitude (second regionRe2) is touched has a next highest peak value. The peak value of aresponse waveform in a case where both points are touched simultaneouslyis decreased most and is a minimum. The detecting circuit 8 can identifya region that has been touched by detecting the level differences whilechanging the reference voltage (threshold value Vt) of the comparator 85in FIG. 5.

In an example shown in FIG. 8, one more region, that is, a third regionRe3 is added.

A third set EU13 of driving electrodes is provided in the third regionRe3. The contact driving scanning section 11 (see FIGS. 4A to 4D)applies a driving voltage of largest amplitude to the driving electrodesof the third set EU13.

In FIG. 8, a point of contact of a finger 100 with a same detecting linein the first region Re1 is indicated as point Y1, a point of contact ofthe finger 100 with the same detecting line within the second region Re2is indicated as point Y2, and a point of contact of the finger 100 withthe same detecting line within the third region Re3 is indicated aspoint Y3. Supposing that a driving voltage at point Y1 is “V₁,” analternating-current pulse of an amplitude “2×V₁” is applied at point Y2,and an alternating-current pulse of an amplitude “3×V₁” is applied atpoint Y3.

When the detection voltage of the detecting line in the voltage detectorDET is decreased from A₁ to B₁ (<A₁) at a time of contact with onlypoint Y1, the ratio of the changing voltage (hereinafter referred to asa rate of change) is set as “b (=B₁/A₁).” In this case, the potential ofthe detecting line changes at the same rate of change b at a time ofcontact with only point Y2 and at a time of contact with only point Y3.

On the other hand, the peak value of a response waveform in a case whereno contact is made with any point (untouched) is 6A₁ (=A₁+2A₁+3A₁) as atotal of the peak values of the three kinds of driving voltages. Whencontact is made simultaneously at a plurality of points, a differentpotential change occurs according to a combination of the points.

FIG. 9 shows potential changes (potential decreases) in all combinationsin an overlapped state.

From FIG. 9, a combination in which contact has occurred can be uniquelydetermined by the level of a potential decrease in the detecting line.This level recognition can also be performed by changing the referencevoltage (threshold value Vt) of the comparator 85 in FIG. 5, forexample.

Third Embodiment

Two sets EU2 of k detecting lines are provided in the presentembodiment.

FIG. 10 shows response waveforms in a case of opposite-phase driving.FIG. 11 shows response waveforms in a case of in-phase driving.

The third embodiment is the same as the first and second embodiments inthat the third embodiment has a set of detecting lines that intersect afirst region Re1 and a second region Re2 in a same manner (which setwill hereinafter be referred to as a first set EU21), as shown in FIG.10 and FIG. 11. The present embodiment is further provided with anotherset of k detecting lines that intersect only the second region Re2. Thek additional detecting lines will hereinafter be referred to as a secondset EU22 of detecting lines.

A detecting circuit 8 a including k voltage detectors DETa is connectedto one end of the first set EU21 of detecting lines. Similarly, adetecting circuit 8 b including k voltage detectors DETb is connected toone end of the second set EU22 of detecting lines. A constitutionincluding the detecting circuits 8 a and 8 b corresponds to anembodiment of “two detecting sections.”

When the two sets of detecting lines intersecting the regions indifferent manners are thus provided, and further the detectors areprovided separately for each set of detecting lines, response waveformsappearing in the inputs of the detectors as shown in FIG. 10 areobtained.

Response waveforms similar to those of FIG. 6 are obtained in thevoltage detectors DETa.

On the other hand, in the voltage detectors DETb, positive responsewaveforms are obtained at a time of non-contact (untouched) and at atime of contact with point A, and positive response waveforms decreasedin potential from the positive response waveforms obtained at a time ofnon-contact (untouched) and at a time of contact with point A areobtained at a time of contact with point B and at a time of contact withpoints A+B. In this case, the maximum peak value of detection voltagediffers between point A and point B. This is because the detecting linesconnected to the voltage detectors DETa and DETb, respectively, aredifferent from each other in length, and are consequently different fromeach other in load capacitance. In FIG. 10, a maximum peak value atpoint A is denoted by a reference “A₁,” and a maximum peak value atpoint B is denoted by a reference “B₁.”

The third embodiment has an advantage of being able to distinguishespecially points A+B and non-contact (untouched) from each other morereliably than the first embodiment.

FIG. 11 represents a case where the opposite-phase driving of FIG. 10 ischanged to in-phase driving.

Also in this case, as in FIG. 10, the maximum peak value of detectionvoltage differs between the voltage detectors DETa and DETb due todifference in load capacitance which difference is caused by the lengthsof the detecting lines. Also in this case, a maximum peak value at pointA is denoted by a reference “A₁,” and a maximum peak value at point B isdenoted by a reference “B₁.” A driving voltage amplitude is denoted byV₁.

In a case of non-contact (untouched) with both of point A and point B,the detection voltage input to a voltage detector DETa maintains themaximum peak value A₁, and the detection voltage input to a voltagedetector DETb maintains the maximum peak value B₁.

In a case of contact with only point A, the detector DETb does notchange a state of output of the maximum peak value B₁, but the detectionvoltage of the detector DETa decreases from the maximum peak value A₁ ata rate of change f (0<f<1).

In a case of contact with only point B, the detector DETb also decreasesthe detection voltage from the maximum peak value B₁ at the rate ofchange f.

In a case of simultaneous contact with point A and point B, thedetection voltage of the detector DETa is further decreased from that inthe case of contact with only point B at the rate of change f. Thedetection voltage input to the detector DETa at this time is observed todecrease from the initial maximum peak value A₁ at a rate of 2f.

Thus, the driving method illustrated in FIG. 11 also has an advantage ofbeing able to distinguish the four cases as combinations of contact andnon-contact reliably.

FIGS. 4A to 4D and FIG. 5 of the first embodiment are applicable also tothe third embodiment except for differences in the manner of overlappingof such detecting lines and the manner of driving.

Incidentally, the third embodiment and the second embodiment can becombined with each other arbitrarily.

Thus, “the detecting section can identify a region where contact hasoccurred on the basis of a pattern of voltage change in a detecting linewhich pattern occurs according to difference in at least one of themanner of intersection of the detecting line and the manner of drivingbetween regions.”

Fourth Embodiment

FIG. 12 is a diagram of a constitution of a fourth embodiment.

In a driving method illustrated in FIG. 12, a set of k detecting linesin a first region Re1 is completely separated from a set of k detectinglines in a second region Re2. For example, a detecting circuit 8 a isconnected to the detecting lines on the first region Re1 side, and adetecting circuit 8 b is connected to the detecting lines on the secondregion Re2 side. Thus, as shown in FIG. 12, the two detecting circuits 8a and 8 b are desirably disposed on both sides in a scanning direction.

In the fourth embodiment, though driving voltage is the same,combinations of the detecting lines and the detecting circuits are inseparate systems, so that a region in which contact has been made can bedetermined easily.

When applied to a display panel, however, the fourth embodiment tends tobe wasteful of a space for arranging the detecting circuits.Specifically, there is a desire to maximize an effective display area ofa display panel and to minimize a frame space of the display panel. Thisdesire is strong especially for a display panel included in a smallelectronic device. Generally, in order to save the frame space, signalsand voltages are often input and output between the display panel andthe outside en bloc from one side (one edge side) of the display panelby a flexible board or the like.

The arrangement of the detecting circuits in FIG. 12 poorly matches withsuch an input-output form. When it is not possible to arrange the twodetecting circuits on both sides as in FIG. 12, wiring to one detectingcircuit needs to be routed by half an outer circumference of the displaypanel. However, there is a fear of a minute signal potential beingaffected by noise and thus an S/N ratio being lowered. Therefore, anadditional circuit load such as an increase in signal amplificationfactor of the detecting circuits 8 or the like is imposed.

However, a method according to the present embodiment is a simplest andreliable method in regard to region determination, and is suitable whena degree of freedom of arrangement of the detecting circuits is high.

Fifth Embodiment

In a fifth embodiment, the function of a touch panel is included withina liquid crystal display panel. In this case, desirably, a part ofdisplay driving electrodes serve also as a detection driving electrode.In addition, a device that prevents detection driving from affectingdisplay is necessary.

Incidentally, the present embodiment can be arbitrarily combined withthe first to fourth embodiments described above. The operation indetection driving has already been described. Thus, the operation andthe constitution of a display device will be described below in detail.

A liquid crystal display device has an electrode (counter electrode) towhich a common driving signal Vcom providing a reference voltage for asignal voltage for gradation display in each pixel is applied as anelectrode common to a plurality of pixels. In the present embodiment,this counter electrode is used also as an electrode for sensor driving.

FIG. 13 is a diagram of an equivalent circuit of a pixel. FIGS. 14A,14B, 14C, and 14D are schematic plan views and a schematic sectionalview of the display panel.

In the liquid crystal display device 1, the pixel PIX shown in FIG. 13is arranged in the form of a matrix.

As shown in FIG. 13, each pixel PIX has a thin film transistor (TFT)(hereinafter written as a TFT 23) as a selecting element of the pixel,an equivalent capacitance C6 of a liquid crystal layer 6, and a storagecapacitor (referred to also as an additional capacitance) Cx. Anelectrode on one side of the equivalent capacitance C6 representing theliquid crystal layer 6 is a pixel electrode 22 separated for each pixeland arranged in the form of a matrix. An electrode on the other side ofthe equivalent capacitance C6 is a counter electrode 43 common to aplurality of pixels.

The pixel electrode 22 is connected to one of the source and the drainof the TFT 23. A signal line SIG is connected to the other of the sourceand the drain of the TFT 23. The signal line SIG is connected to ahorizontal driving circuit not shown in the figure. A video signalhaving a signal voltage is supplied from the horizontal driving circuitto the signal line SIG.

The counter electrode 43 is supplied with a common driving signal Vcom.The common driving signal Vcom is generated by inverting a positive ornegative potential with a central potential as a reference in eachhorizontal period (1H).

The gate of the TFT 23 is electrically made common to all pixels PIXarranged in a row direction, that is, a horizontal direction of adisplay screen, whereby a scanning line SCN is formed. The scanning lineSCN is supplied with a gate pulse for opening and closing the gate ofthe TFT 23, which gate pulse is output from a vertical driving circuitnot shown in the figure. Therefore the scanning line SCN is referred toalso as a gate line.

As shown in FIG. 13, the storage capacitor Cx is connected in parallelwith the equivalent capacitance C6. The storage capacitor Cx is providedto prevent a shortage of accumulating capacitance with the equivalentcapacitance C6 alone and a decrease in writing potential due to aleakage current of the TFT 23 or the like. The addition of the storagecapacitor Cx also contributes to the prevention of flicker and theimprovement of uniformity of screen luminance.

As viewed in a sectional structure (FIG. 14D), the liquid crystaldisplay device 1 in which such pixels are arranged has a substrate thatincludes the TFT 23 shown in FIG. 13, the TFT 23 being formed in aposition not appearing in the section, and which is supplied with adriving signal (signal voltage) for the pixels (which substrate willhereinafter be referred to as a driving substrate 2). The liquid crystaldisplay device 1 also has a counter substrate 4 disposed so as to beopposed to the driving substrate 2 and a liquid crystal layer 6 disposedbetween the driving substrate 2 and the counter substrate 4.

The driving substrate 2 has a TFT substrate 21 (a substrate body sectionis formed by glass or the like) as a circuit substrate in which the TFT23 in FIG. 13 is formed and a plurality of pixel electrodes 22 arrangedin the form of a matrix on the TFT substrate 21.

A display driver (the vertical driving circuit, the horizontal drivingcircuit and the like) not shown in the figure for driving each pixelelectrode 22 is formed in the TFT substrate 21. In addition, the TFT 23shown in FIG. 13 as well as wiring such as the signal line SIG, thescanning line SCN and the like is formed in the TFT substrate 21. Thedetecting circuit 8 for performing touch detecting operation (FIG. 5)and the like may be formed in the TFT substrate 21.

The counter substrate 4 has a glass substrate 41, a color filter 42formed on one surface of the glass substrate 41, and the counterelectrode 43 formed on the color filter 42 (liquid crystal layer 6side). The color filter 42 is formed by periodically arranging colorfilter layers of three colors of red (R), green (G), and blue (B), forexample, with each pixel (or each pixel electrode 22) associated withone of the three colors R, G, and B. Incidentally, there are cases wherea pixel associated with one color is referred to as a “sub-pixel” and aset of sub-pixels of the three colors R, G, and B is referred to as a“pixel.” In this case, however, sub-pixels are also written as “pixelsPIX.”

The counter electrode 43 serves also as a sensor driving electrodeforming a part of a touch sensor performing touch detecting operation,and corresponds to the driving electrode E1 in FIGS. 1A and 1B and FIGS.2A and 2B.

The counter electrode 43 is connected to the TFT substrate 21 by acontact conductive column 7. The common driving signal Vcom of analternating-current pulse waveform is applied from the TFT substrate 21to the counter electrode 43 via the contact conductive column 7. Thiscommon driving signal Vcom corresponds to the AC pulse signal Sgsupplied from the driving signal source S in FIGS. 1A and 1B and FIGS.2A and 2B.

A detecting line 44 (44_1 to 44 _(—) k) is formed on the other surface(display surface side) of the glass substrate 41, and a protective layer45 is formed on the detecting line 44. The detecting line 44 forms apart of the touch sensor, and corresponds to the detecting electrode E2in FIGS. 1A and 1B and FIGS. 2A and 2B. A detecting circuit DET (FIG. 5)for performing touch detecting operation may be formed in the glasssubstrate 41.

The liquid crystal layer 6 modulates light passing through the liquidcrystal layer 6 in a direction of thickness (direction in which theelectrodes are opposed to each other) according to a state of anelectric field applied to the liquid crystal layer 6 as a “displayfunctional layer.” As the liquid crystal layer 6, liquid crystalmaterials in various modes such as TN (Twisted Nematic), VA (VerticalAlignment), and ECB (Electrically Controlled Birefringence), forexample, are used.

Incidentally, alignment films are respectively disposed between theliquid crystal layer 6 and the driving substrate 2 and between theliquid crystal layer 6 and the counter substrate 4. In addition,polarizers are respectively disposed on the non-display surface side(that is, the back side) of the driving substrate 2 and on the displaysurface side of the counter substrate 4. These optical functional layersare not shown in FIGS. 14A to 14D.

As shown in FIG. 14A, the counter electrode 43 is divided in a directionof rows or columns of a pixel arrangement, or a column direction(vertical direction of the figure) in the present example. The directionof this division corresponds to a direction of scanning of pixel linesin display driving, that is, a direction in which a vertical drivingcircuit not shown in the figure sequentially activates scanning linesSCN.

The counter electrode 43 is divided into n pieces in total from a needfor the counter electrode 43 to serve also as driving electrode. Thus,counter electrodes 43_1, 43_2, . . . , 43 _(—) m, . . . , 43 _(—) n arearranged in the form of a plane having a stripe-shaped pattern that islong in a row direction, and are spread all over in parallel with eachother with a clearance from each other within the plane.

At least two or more counter electrodes, or m (<n) counter electrodes ofthe n divided counter electrodes 43_1 to 43 _(—) n are drivensimultaneously. That is, a common driving signal Vcom is applied to mcounter driving electrodes 43_1 to 43 _(—) m simultaneously, and thepotential of the common driving signal Vcom repeats inversion in eachhorizontal period (1H). At this time, other counter electrodes do notvary in potential because the other counter electrodes are not suppliedwith the driving signal. In the present embodiment, a bundle of counterelectrodes driven simultaneously will be written as analternating-current driven electrode unit EU.

In the present embodiment, the number of counter electrodes in eachalternating-current driven electrode unit EU is a fixed number m. Inaddition, the alternating-current driven electrode unit EU shiftsstepwise in the column direction while changing a combination of thebundled counter electrodes. That is, the combination of counterelectrodes selected as the alternating-current driven electrode unit EUchanges in each shift. In two shifts, only one divided counter electrodeis removed from the selection, and a divided counter electrode is newlyselected instead.

The n counter driving electrodes 43_1 to 43 _(—) n are thus arranged atequal distances by the number of pixels in the column direction. WhenVcom alternating-current driving is repeated, the n counter drivingelectrodes 43_1 to 43 _(—) n shift the combination of m (<n) counterelectrodes selected as one alternating-current driven electrode unit EUwith a pitch at which counter electrodes are arranged in the columndirection as a unit. The “pitch of counter electrodes” in this case is adistance obtained by totaling the width of a counter electrode in thecolumn direction and a clearance to another counter electrode adjacenton one side in the direction of the width. The pitch of counterelectrodes in the column direction is generally equal to a pixel size inthe column direction.

The Vcom driving with the alternating-current driven electrode unit EUof such counter electrodes and the shift operation are performed by aVcom driving circuit 9 as a “display driving scanning section” providedwithin the vertical driving circuit (writing driving scanning section)not shown in the figure. The operation of the Vcom driving circuit 9 canbe considered to be equal to an “operation of moving a driving signalsource S (see FIGS. 1A and 1B and FIGS. 2A and 2B) for performingsimultaneous Vcom alternating-current driving of wiring of m counterelectrodes in the column direction and scanning the selected counterelectrodes in the column direction while changing the selected counterelectrodes one by one.”

Incidentally, FIG. 14A and FIG. 14B are diagrams divided for thedescription of electrode patterns. In actuality, however, the counterelectrodes 43_1 to 43 _(—) m and the detecting lines (detectingelectrodes 44_1 to 44 _(—) k) are arranged in such a manner as tooverlap each other as shown in FIG. 14C, thus enabling positiondetection in a two-dimensional plane.

With this constitution, the detecting circuit 8 can detect a position inthe row direction on the basis of which voltage detector DET shows achange in voltage, and obtain information on a position in the columndirection on the basis of timing of the detection.

The shifting of counter electrodes 43 and alternating-current driving bythe Vcom driving circuit 9 having the above driving signal source S as abasic constitution will next be described with reference to drawings.

FIG. 15A shows the counter electrodes 43_1 to 43 _(—) n divided in pixeldisplay line units (referred to also as writing units). FIG. 15B is adiagram of an equivalent circuit of a touch sensor section at a time ofdriving the counter electrode 43_1 as the first one of the counterelectrodes 43_1 to 43 _(—) n.

As shown in FIG. 15A, the driving signal source S is connected to thecounter electrode 431, and is performing Vcom alternating-currentdriving of the counter electrode 43_1. At this time, the touch sensorsection has an equivalent circuit formed as shown in FIG. 15B, asalready described. The capacitance value of each of capacitive elementsC1_1 to C1 _(—) n is denoted by “Cp,” a capacitive component (parasiticcapacitance) connected to the detecting electrode 44 other than thecapacitive elements C1_1 to C1 _(—) n is denoted by “Cc,” and theeffective value of alternating voltage of the driving signal source S isdenoted by “V1.”

A detection signal Vdet detected in the voltage detector DET at thistime is a voltage Vs when a finger is not in contact, and is a voltageVf when a finger is in contact. The voltages Vs and Vf will hereinafterbe referred to as a sensor voltage.

The sensor voltage Vs at the time of non-contact is expressed by anequation as shown in FIG. 15C. This equation shows that when the numbern of divisions of the counter electrode 43 is large, each capacitancevalue Cp is correspondingly decreased. While the denominator of theequation of FIG. 15C does not change very much because “nCp” issubstantially fixed, the numerator is decreased. Thus, as the number nof divisions of the counter electrode 43 is increased, the magnitude(alternating-current effective value) of the sensor voltage Vs isdecreased.

Therefore the number n of divisions cannot be made very large.

On the other hand, if the number n of divisions is small and the area ofone counter electrode 43_1 is large, a slight potential variation(transient potential variation) when the Vcom alternating-currentdriving changes between electrodes is seen as a line on a displayscreen.

Accordingly, as described above, the present embodiment performsdivision itself in each pixel display line (writing unit), but performssimultaneous Vcom alternating-current driving of a plurality of counterelectrodes. In addition, a part of the divided counter electrodes areselected two consecutive times. Thereby, a decrease in sensor voltage(decrease in S/N ratio) due to an increase in the number n of divisionsand dilution (obscuring) of the potential variation at the time ofelectrode changes are achieved simultaneously.

FIGS. 16A, 16B, and 16C are diagrams of assistance in explaining theoperation of the alternating-current driving and shifting.

Seven counter electrodes indicated by hatching in FIGS. 16A to 16C forman alternating-current driven electrode unit EU. FIGS. 16A to 16C show achange of selection ranges when the alternating-current driven electrodeunit EU is shifted in units of one pixel line in the column direction.

At time T1 in FIG. 16A, while the first writing unit is not selected,the counter electrodes corresponding to the second to eighth lines areselected and subjected to simultaneous alternating-current driving bythe driving signal source S. In a next cycle (time T2), a shift isperformed by one writing unit, so that the two counter electrodescorresponding to the first and second lines are not selected, the sevenelectrodes from the third electrode on down are selected, and the othersare not selected. Further, in a next cycle (time T3), a shift is furtherperformed by one writing unit, so that the counter electrodescorresponding to the first to third lines are not selected, the sevenelectrodes from the fourth electrode on down are selected, and theothers are not selected.

Thereafter the shifting and the alternating-current driving aresimilarly repeated.

This operation reduces the value n in the equation shown in FIG. 15C to1/7 of the real number of divisions, and correspondingly increases theeffective value of the sensor voltage Vs. On the other hand, as shown inFIGS. 16A to 16C, a unit newly included in the selected group and a unitexcluded in place of the newly included unit are one counter electrodecorresponding to one pixel line. Thus, the changing frequency of thealternating-current driving is equal to the 1H inversion frequency ofthe common driving signal Vcom. This frequency is a very high frequencyobtained by multiplying the frequency of commercial power, for example60 [Hz] by the number of pixels in the column direction. When the numberof pixels in the column direction is 480, for example, the frequency is28.8 [kHz], and the frequency of a pulse waveform is half the frequencyof 28.8 [kHz], that is, 14.4 [kHz]. Thus, image changes caused by shiftsin the alternating-current driving have a sufficiently high frequencyinvisible to the eye of a human.

Thus, the prevention of a decrease in S/N ratio due to a decrease insensor voltage and the prevention of a degradation in image quality dueto changes in electrode driving are made compatible with each other.

The operation of the display device formed as described above will nextbe described.

The display driver (the horizontal driving circuit and the verticaldriving circuit not shown in the figure or the like) of the drivingsubstrate 2 supplies each electrode pattern (counter electrodes 431 to43 _(—) n) of the counter electrode 43 with the common driving signalVcom on a line-sequential basis. The manner of selecting counterelectrodes and the manner of shifting at this time are as describedabove. The common driving signal Vcom is used also to control thepotential of the counter electrodes for image display.

In addition, the display driver supplies a signal voltage to the pixelelectrode 22 via the signal line SIG, and controls the switching of theTFT for each pixel electrode on a line-sequential basis via the scanningline SCN in synchronism with the supply of the signal voltage. Thereby,an electric field in a vertical direction (direction perpendicular tothe substrates) which electric field is determined by the common drivingsignal Vcom and each pixel signal is applied to the liquid crystal layer6 in each pixel, whereby a liquid crystal state in the liquid crystallayer 6 is modulated. Display is thus made by so-called inversiondriving.

Meanwhile, on the side of the counter substrate 4, a capacitive elementC1 is formed in each part of intersection of each electrode pattern(counter electrodes 43_1 to 43 _(—) n) of the counter electrode 43 andeach electrode pattern (detecting electrodes 441 to 44 _(—) k) of thedetecting electrode 44. When the common driving signal Vcom issequentially applied to each electrode pattern of the counter electrode43 on a time division basis, each of capacitive elements C1 of one rowwhich capacitive elements C1 are formed in parts of intersection of theelectrode pattern of the counter electrode 43 to which the commondriving signal Vcom is applied and each electrode pattern of thedetecting electrode 44 is charged or discharged. As a result, adetection signal Vdet of a magnitude corresponding to the capacitancevalue of the capacitive element C1 is output from each electrode patternof the detecting electrode 44. In a state of a finger of a user nottouching the surface of the counter substrate 4, the magnitude of thedetection signal Vdet is substantially fixed (sensor voltage Vs). Withthe scanning of the common driving signal Vcom, the row of capacitiveelements C1 to be charged or discharged moves on a line-sequentialbasis.

When the finger of the user touches a position of the surface of thecounter substrate 4, a capacitive element C2 formed by the finger isadded to the capacitive element C1 originally formed at the touchposition. As a result, the value (sensor voltage Vs) of the detectionsignal Vdet at a point in time when the touch position is scannedbecomes lower than that of other positions (the value becomes a sensorvoltage Vf (<Vs)). The detecting circuit 8 (FIG. 5) compares thedetection signal Vdet with a threshold value Vt, and determines that theposition is a touch position when the detection signal Vdet is equal toor lower than the threshold value Vt. The touch position can bedetermined from timing of application of the common driving signal Vcomand timing of detection of the detection signal Vdet equal to or lowerthan the threshold value Vt.

Thus, according to the present embodiment, the common electrode (counterelectrode 43) for liquid crystal driving which electrode is originallyprovided in a liquid crystal display element is used also as one(driving electrode) of a pair of electrodes for a touch sensor whichelectrodes are composed of the driving electrode and the detectingelectrode. In addition, according to the present embodiment, the commondriving signal Vcom as a display driving signal is shared as a touchsensor driving signal, whereby a capacitance type touch sensor isformed. Thus, only the detecting electrode 44 needs to be newlyprovided, and the touch sensor driving signal does not need to be newlyprovided. Therefore the constitution is simple.

In addition, a plurality of counter electrodes are simultaneouslysubjected to alternating-current driving, and the group of electrodessimultaneously subjected to alternating-current driving is shifted suchthat each counter electrode is selected at both of two times ofalternating-current driving. Thus, the prevention of a decrease in S/Nratio of the detection voltage of the sensor and the prevention of adegradation in image quality are made compatible with each other.

Further, the driving electrode and the driving circuit for the commondriving signal Vcom can be used also as the sensor driving electrode anddriving circuit, so that arrangement space and power consumption can becorrespondingly saved.

Incidentally, in FIGS. 4A to 4D and FIG. 6, the detecting electrode 44is shown as a line of a small width. However, the detecting electrode 44may be formed with a large width in the row direction. A case where thecapacitance value of the capacitive element C1 is too small and isdesired to be increased can be dealt with by increasing the electrodewidth. Conversely, a case where the capacitance value of the capacitiveelement C1 is too large because of a thin dielectric D, for example, andis desired to be decreased can be dealt with by decreasing the electrodewidth.

In addition, the identification of a region in the foregoing first tofourth embodiments is also made possible by changing the width of thedetecting electrode 44 (detecting line E2) in the regions.

In the fifth embodiment, the group of counter electrodes drivensimultaneously (alternating-current driven electrode unit EU) is shiftedby each pitch of divided counter electrodes. However, the presentinvention is not limited to this.

Further, in the sectional structure, the detecting electrode 44 may beformed at a position such that the detecting electrode 44 is opposed tothe counter electrode 43 with the color filter 42 interposed between thedetecting electrode 44 and the counter electrode 43.

Sixth Embodiment

A sixth embodiment will next be described. Unlike the fifth embodiment,the present embodiment uses a liquid crystal element in a transverseelectric field mode as a display element.

FIG. 17 is a schematic sectional view of a structure of a display deviceaccording to the present embodiment. In FIG. 17, the same constitutionsas in the fifth embodiment are identified by the same referencenumerals, and description thereof will be omitted as appropriate.

As far as the position of electrodes is concerned (patterns aredifferent), the display device according to the present embodiment isdifferent from the fifth embodiment in that a counter electrode 43 isdisposed on the side of a driving substrate 2. The counter electrode 43in the present embodiment is disposed so as to be opposed to pixelelectrodes 22 on an opposite side of the pixel electrodes 22 from aliquid crystal layer 6. While the word “opposite” is used, though notspecifically shown in the figure, a relatively long distance between thepixel electrodes 22 is secured, and the counter electrode 43 makes anelectric field act on the liquid crystal layer 6 from between the pixelelectrodes 22. That is, liquid crystal display in the transverseelectric field mode in which the direction of the electric field actingon the liquid crystal layer 6 is a horizontal direction is made.

The other constitutions of the sixth embodiment and the fifth embodimentare the same as long as arrangement in section is concerned.

A capacitive element C1 is formed between a detecting electrode 44 andthe counter electrode 43, and thus has a lower capacitance value than inthe fifth embodiment (FIG. 14D). However, such a measure as compensatingfor an increase in electrode interval by increasing electrode width, forexample, can be taken, and sensitivity may be increased in relation to acapacitive element C2.

The liquid crystal layer 6 modulates light passing through the liquidcrystal layer 6 according to the state of the electric field. A liquidcrystal in the transverse electric field mode such for example as an FFS(Fringe Field Switching) mode or an IPS (In-Plane Switching) mode isused as the liquid crystal layer 6.

More detailed description will next be made with reference to FIGS. 18Aand 18B.

In the liquid crystal element in the FFS mode shown in FIGS. 18A and18B, the pixel electrode 22 patterned into a comb-tooth shape isdisposed over the counter electrode 43 formed on the driving substrate 2via an insulating layer 25, and an alignment film 26 is formed so as tocover the pixel electrodes 22. The liquid crystal layer 6 is sandwichedbetween the alignment film 26 and an alignment film 46 on the side of acounter substrate 4. Two polarizers 24 and 45 are disposed in acrossed-Nicol state. The rubbing direction of the two alignment films 26and 46 coincides with the transmission axis of one of the two polarizers24 and 45. FIGS. 18A and 18B show a case where the rubbing directioncoincides with the transmission axis of a protective layer 45 on anemitting side. Further, the rubbing direction of the two alignment films26 and 46 and the direction of the transmission axis of the protectivelayer 45 are set substantially parallel to the extending direction ofthe pixel electrodes 22 (direction of length of the comb teeth) in arange in which the direction of rotation of liquid crystal molecules isdefined.

The operation of the display device formed as described above will nextbe described.

Principles of display operation of the liquid crystal element in the FFSmode will first be described briefly with reference to FIGS. 18A and 18Band FIGS. 19A and 19B. FIGS. 19A and 19B show a section of principalparts of the liquid crystal element in an enlarged state. Of thesefigures, FIGS. 18A and 19A show a state of the liquid crystal element ata time of non-application of an electric field, and FIGS. 18B and 19Bshow a state of the liquid crystal element at a time of application ofan electric field.

In a state in which no voltage is applied between the counter electrode43 and the pixel electrodes 22 (FIG. 18A and FIG. 19A), the axis of theliquid crystal molecules 61 forming the liquid crystal layer 6 isorthogonal to the transmission axis of the polarizer 24 on an incidenceside, and is parallel to the transmission axis of the protective layer45 on the emitting side. Therefore, incident light h that has passedthrough the polarizer 24 on the incidence side reaches the protectivelayer 45 on the emitting side without a phase difference occurringwithin the liquid crystal layer 6, and is absorbed in the protectivelayer 45, thus resulting in black display. On the other hand, in a statein which a voltage is applied between the counter electrode 43 and thepixel electrodes 22 (FIG. 18B and FIG. 19B), the direction of alignmentof the liquid crystal molecules 61 is rotated to an oblique directionwith respect to the extending direction of the pixel electrodes 22 by atransverse electric field E occurring between the pixel electrodes 22.The intensity of the electric field at a time of white display isoptimized such that the liquid crystal molecules 61 positioned at thecenter of the liquid crystal layer 6 in the direction of thickness ofthe liquid crystal layer 6 are rotated by about 45 degrees at this time.Thereby, a phase difference occurs in the incident light h that haspassed through the polarizer 24 on the incidence side while the incidentlight h passes through the inside of the liquid crystal layer 6, and theincident light h becomes linearly polarized light rotated by 90 degreesand passes through the protective layer 45 on the emitting side, thusresulting in white display.

Incidentally, as for a touch sensor section, only the electrodearrangement in the sectional structure is different, and basic operationis the same as in the first to fourth embodiments. Specifically, thecounter electrode 43 is driven in a column direction by repeating Vcomalternating-current driving and shifting, and a difference betweensensor voltages Vs and Vf at this time is read via a voltage detectorDET. The sensor voltage Vs read as a digital value is compared with athreshold value Vt, and the position of contact or proximity of a fingeris detected in the form of a matrix.

At this time, as in the first embodiment, as shown in FIGS. 16A to 16C,m counter electrodes 43 (m=7 in FIGS. 16A to 16C) are simultaneouslysubjected to alternating-current driving, and are shifted by one counterelectrode 43 corresponding to one writing unit. Then alternating-currentdriving is performed again. This shifting and alternating-currentdriving are repeated. Thus, the value n in the equation shown in FIG.15C is reduced to 1/m of the real number of divisions, and the sensorvoltage Vs is correspondingly increased. On the other hand, as shown inFIGS. 16A to 16C, a unit newly included in the selected group and a unitexcluded in place of the newly included unit are one counter electrodecorresponding to one pixel line. Thus, the changing frequency of thealternating-current driving is equal to the 1H inversion frequency ofthe common driving signal Vcom. This frequency is a very high frequencyobtained by multiplying the frequency of commercial power, for example60 [Hz] by the number of pixels in the column direction. When the numberof pixels in the column direction is 480, for example, the frequency is28.8 [kHz], and the frequency of a pulse waveform is half the frequencyof 28.8 [kHz], that is, 14.4 [kHz], which is a sufficiently highfrequency invisible to the eye of a human.

Thus, the prevention of a decrease in S/N ratio due to a decrease insensor voltage and the prevention of a degradation in image quality dueto changes in electrode driving are made compatible with each other.

In addition to the above effects, as in the fifth embodiment, there isan advantage of a simple constitution as a result of sharing anelectrode for Vcom driving and sensor driving. Further, the drivingelectrode and the driving circuit for the common driving signal Vcom canbe used also as sensor driving electrode and driving circuit, so thatarrangement space and power consumption can be correspondingly saved.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2008-236931 filedin the Japan Patent Office on Sep. 16, 2008, the entire content of whichis hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alternations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalent thereof.

What is claimed is:
 1. A contact detecting device comprising: a contactresponding section configured to produce an electric change in responseto an object to be detected coming into contact with or in proximity toa detecting surface; a contact driving scanning section configured toscan application of driving voltage to said contact responding sectionin one direction within said detecting surface, and control output ofsaid electric change in time series; and a detecting section configuredto detect occurrence of said electric change from a voltage change in adetection line group, and identify a position of the occurrence, whereinsaid contact driving scanning section performs a plurality of scans ofdifferent regions of said contact responding section in parallel witheach other, and outputs a plurality of said electric changes in parallelwith each other, the contact responding section includes a plurality ofdetection lines that each corresponds to a region of the differentregions of said contact responding section, each of the plurality ofdetection lines having a longitudinal length different from each otheraccording to the different regions of said contact responding section,and the smaller a distance in a direction along the longitudinal lengthbetween the detecting section and the region, the shorter thelongitudinal length of the detection line for the corresponding region.2. The contact detecting device according to claim 1, wherein at leastone of a manner of intersecting said plurality of regions of saidcontact responding section by said detection line group and a manner ofdriving said plurality of regions by said contact driving scanningsection differs between said regions, and said detecting sectionidentifies one of said plurality of regions with which region saidobject to be detected is in contact or to which region said object to bedetected is in proximity on a basis of a voltage change of a detectionline, the voltage change occurring according to difference in at leastone of the manner of said intersecting and the manner of said drivingbetween said regions.
 3. The contact detecting device according to claim2, wherein at least one of a phase and an amplitude of said drivingvoltage output by said contact driving scanning section differs betweensaid plurality of regions, and said detecting section is connected toone end in said scanning direction of said detecting group andidentifies one of said plurality of regions with which region saidobject to be detected is in contact or to which region said object to bedetected is in proximity on the basis of the voltage change of thedetecting line.
 4. The contact detecting device according to claim 3,wherein a predetermined number of detecting lines are arranged so as tosimilarly intersect two regions of said contact responding section, andsaid contact driving scanning section supplies said driving voltagesinverted from each other in phase by 180 degrees to said two regions. 5.The contact detecting device according to claim 3, wherein apredetermined number of detecting lines are arranged so as to similarlyintersect a plurality of regions of said contact responding section, andsaid contact driving scanning section supplies said driving voltages ofdifferent amplitudes to said plurality of regions.
 6. The contactdetecting device according to claim 3, wherein two sets of apredetermined number k (≧2) of detecting lines are arranged for tworegions of said contact responding section, one set of detecting linesbeing arranged so as to intersect one region, and the two sets ofdetecting lines being arranged so as to intersect the other region, andsaid contact driving scanning section supplies said driving voltagesinverted from each other in phase by 180 degrees to said one region andsaid other region.
 7. The contact detecting device according to claim 3,wherein N (≧2) sets of a predetermined number k (≧2) of detecting linesare arranged for N regions of said contact responding section, numbersof sets of detecting lines overlapping said plurality of regions,respectively, being different from each other, and said contact drivingscanning section supplies said driving voltages of different amplitudesto said plurality of regions.
 8. The contact detecting device accordingto claim 1, further comprising: two sets of a predetermined number ofdetecting lines, the detecting lines being long in a scanning directionof said contact responding section and being in a form of parallelstripes; and two detecting sections each connected to said predeterminednumber of detecting lines of the corresponding set at one end in saidscanning direction, the two detecting sections each detecting occurrenceof said electric change on a basis of a voltage change pattern occurringin the predetermined number of detecting lines of the corresponding setand identifying a position of the occurrence.
 9. A display devicecomprising: a display section configured to provide light modulationaccording to an input video signal, and output light after themodulation from a display surface; a display driving scanning sectionhaving a plurality of pixel lines, the display driving scanning sectionconfigured to perform a scan operation of applying driving voltage forsaid light modulation to each pixel line in a direction orthogonal tothe pixel lines; and a detecting section configured to detect occurrenceof said electric change from a voltage change in a detection line group,and identify a position of the occurrence; and a contact respondingsection configured to produce an electric signal change in response toan object to be detected coming into contact with or proximity to saiddisplay surface is formed within said display section, wherein saiddisplay driving scanning section doubles as a contact driving scanningsection configured to scan application of driving voltage to saidcontact responding section in one direction within said display surface,and control output of said electric signal change in time series, andsaid contact driving scanning section performs a plurality of scans ofdifferent regions of said contact responding section in parallel witheach other, and outputs a plurality of said electric signal changes inparallel with each other, the contact responding section includes aplurality of detection lines that each corresponds to a region of thedifferent regions of said contact responding section, each of theplurality of detection lines having a longitudinal length different fromeach other according to the different regions of said contact respondingsection, and the smaller a distance in a direction along thelongitudinal length between the detecting section and the region, theshorter the longitudinal length of the detection line for thecorresponding region.
 10. The display device according to claim 9,wherein at least one of a manner of intersecting said plurality ofregions of said contact responding section by said detection line groupand a manner of driving said plurality of regions by said contactdriving scanning section differs between said regions, and saiddetecting section identifies one of said plurality of regions with whichregion said object to be detected is in contact or to which region saidobject to be detected is in proximity on a basis of a voltage change ofa detection line, the voltage change occurring according to differencein at least one of the manner of said intersecting and the manner ofsaid driving between said regions.
 11. The display device according toclaim 10, wherein at least one of a phase and an amplitude of saiddriving voltage output by said contact driving scanning section differsbetween said plurality of regions, and said detecting section isconnected to one end in said scanning direction of said detecting linegroup and identifies one of said plurality of regions with which regionsaid object to be detected is in contact or to which region said objectto be detected is in proximity on the basis of the voltage changepattern of the detecting line, the voltage change pattern occurringaccording to difference in said driving voltage.
 12. The displays deviceaccording to claim 9, further comprising: two sets of a predeterminednumber of detecting lines, the detecting lines being long in a scanningdirection of said contact responding section and being in a form ofparallel stripes; and two detecting sections each connected to saidpredetermined number of detecting lines of the corresponding-set at oneend in said scanning direction, the two detecting sections eachdetecting occurrence of said electric signal change on a basis of avoltage change pattern occurring in the predetermined number ofdetecting lines of the corresponding set and identifying a position ofthe occurrence.
 13. The display device according to claim 9, whereinsaid contact responding section is formed by arranging sensors in aplane parallel to said display surface in a form of a matrix, and when arow in a predetermined direction of said sensors is a line within saidcontact responding section, said contact driving scanning sectionperforms scanning with a predetermined number of consecutive said linesas a minimum unit in a direction in which a plurality of said lines arearranged repetitively.